chore(package): update core-js to version 3.6.1

Closes #1397

Author: greenkeeper[bot]

package.json

@@ -80,7 +80,7 @@
     "babel-eslint": "10.0.3",
     "babel-loader": "8.0.6",
     "babel-plugin-transform-object-rest-spread": "6.26.0",
-    "core-js": "3.4.4",
+    "core-js": "3.6.1",
     "cross-env": "6.0.3",
     "css-loader": "3.4.0",
     "eslint": "6.8.0",